by Scott Bowles, USA TODAY

by Scott Bowles, USA TODAY

LOS ANGELES - When it comes to Hollywood salaries, what you make can bear little resemblance to what you're worth.

Such are the findings of a study to be released Tuesday on how much money the industry's biggest names bring to their movies.

A-list stars and directors bring home paychecks that dwarf the measurable dollars they generate for their projects, suggests the "Bankability Index," a study of the financial impact of the film industry by data-crunching firm the-numbers.com. The three-year study examined box office and video revenues of projects involving more than 65,000 Hollywood employees over their careers, from directors to actors, sound designers and set decorators. The figures were adjusted for inflation and weighted based on studio billing, with top stars and directors taking the largest share.

While some of the names near the top of the Index are to be expected - Johnny Depp, Tom Cruise - the extent of their financial impact is surprising.

Director Steven Spielberg tops the list, generating $27.4 million in box-office revenues and video rentals a year, or $13.7 million a movie, the study finds. The prolific actor Samuel L. Jackson is second with $24.4 million ($6.2 million a movie), followed by Depp at $24.3 million ($10.5 million) and Cruise at $24 million ($17.1. million).

Compare that with Forbes' annual list of the industry's highest paid actors. Robert Downey Jr. tops them all at an estimated $75 million for 2013. Yet the Index lists him as only Hollywood's ninth-biggest revenue draw, generating $20.6 million a year for his movies. The next highest paid actors on Forbes' list aren't even on the Index's top 10: Channing Tatum is second at $60 million, followed by Hugh Jackman ($55 million), Mark Wahlberg ($52 million) and Dwayne Johnson ($46 million). As a director, Spielberg wasn't on Forbes' actor list, though celebritynetworth.com estimates Spielberg's annual salary at $150 million.

The study does not address the disparity between salary and worth. Head researcher Bruce Nash of the-numbers.com says the Index examines Hollywood as if it were a single sales firm, with the top salesman, Spielberg, "driving the bottom line more than anyone else, so he would be the top employee. We understand that big names command huge salaries and drive business. We wanted to look at everybody in the industry as if it were one giant, corporate body."

Unheralded employees abound in the business, the study finds.

Take Christopher Boyes, a sound engineer who'd probably get trampled on a red carpet if he stood in front of Depp. But the study finds that Boyes is the 16th-biggest money-generator in Hollywood at $13.5 million a year, designing sound sets for 31 movies, including all of the Pirates of the Caribbean and The Lord of the Rings movies, as well as Avatar and Titanic. "If a movie made more than $400 million, he probably had a hand in making it," Nash says.

Composer Hans Zimmer (Pirates, Man of Steel) has had his baton in a few cash cows, as well. He's No. 6 on the Index, worth $22.6 million a year. "What became clear," Nash says, "was how important the other players are. You can see how important it is to get these prolific talents who fly under the radar."

And for those who fly above it, don't be so quick to judge, says Paul Dergarabedian, box office analyst for entertainment research firm Rentrak.

Remember, he says, Downey anchors two juggernaut franchises in The Avengers and Iron Man. "The studios are making an investment in the future, largely based on personality," he says. "And you really can't put a price on that."